Underground storage tanks of the type found at service stations generally include several riser lines which extend up from the top of the storage tank. A pair of riser lines extend up to ground level for use in filling the underground tank. One line is used for transferring fuel from a fuel tanker to the underground tank and the other line is used to transfer the vapor displaced from the underground tank being filled back to the fuel tanker. A third riser line is provided for use in placing a submersible product pump into the storage tank to permit pumping of the product from the storage tank to the various product dispensers found at the service station.
The pump riser line associated with the pumping equipment of an underground storage tank often leads to a containment box which houses the piping and electrical equipment associated with the submersible product pump. The containment box associated with the pumping equipment is generally accessible through a manhole. This containment box is useful for a number reasons. First, a containment box provides access to the pumping equipment associated with an underground storage tank. Perhaps more importantly, a containment box is useful in that if there is ever any failure of the equipment associated with the product pump such that fuel leaks from the equipment, the containment box will contain the leaking fuel and prevent it from contaminating the surrounding soil.
In addition to containment boxes used in connection with the pumps for the underground storage tanks, service stations generally include other secondary containment equipment useful for containing any leakage of products so as to prevent contamination of the surrounding soil. Examples include tank liners, double-walled piping systems and containment boxes associated with the product dispensers.
While secondary containment systems using double-walled pipes and containment boxes are routinely used to prevent soil contamination at service stations, the use of secondary containment systems for containing leaks at the joints between a storage tank and its riser lines have only recently been proposed. Initial attempts at providing secondary containment at the riser line joints have generally required the use of a secondary riser tube which surrounds a riser line and which is permanently sealed to the outer wall of the tank. While such a system is fairly effective at containing any leaks at the various riser line joints, one problem with such a system is that the sealing of the riser tube to wall of the underground storage tank can be difficult. Often, a joint made of fiberglass and fiberglass resin or similar materials must be used to form an effective seal. However, materials such as fiberglass can be difficult to work with and can require a significant amount of time for the associated resin to cure. They can also result in a brittle joint that is susceptible to cracking upon the settling of the surrounding soil. Of course, a cracked joint is ineffective at containing any leakage. A further problem with such systems is that in order to ensure that the fiberglass or other sealing material provides a good seal against the tank wall, power tools such as sanders or grinders must be used to remove the dirt or other residue that may be found on the tank's outer surface. Such practices are often discouraged by tank manufacturers due to the risk that such procedures might compromise the integrity of the underground storage tank. Consequently, an improved, easy to install secondary containment system is desired for use with underground storage tank riser lines.